Not sure if anyone has seen this yet as I think it was just recently added by the LOC.....but this is a GOLDMINE fella's.

About 20 of Spalding's Base Ball Guides from 1889 to 1939 have been scanned and put online in high resolution.

They have complete team photo sets of each team for that particular year. Some examples from the Detroit Tigers section from the 1910 one:

Each collection also has photo sets of most college teams back then!

I could spend all day on there if I didn't actually have to do...."real world" thing. :-(